Magnetic Bearings Gaining Traction In High-End Apps

Moore's Law is giving a bump to magnetic bearings, enabling the well-known technology to serve in a host of new applications, ranging from chillers on naval vessels to turbomolecular pumps in the semiconductor industry.

"The acceptance of the (magnetic bearing) technology and the ability to apply it in more situations is improving with computing power," said Mark Hinckley, director of the Mechatronics Platform at SKF USA Inc. "It's developing and is becoming more and more applicable to industry."

The technology, which combines sensors and signal processors to magnetically support a spinning motor shaft, is benefiting from electronic performance in its quest to quickly balance machinery forces, Hinckley said. During operation, the bearing's sensors send position information to microprocessors or digital signal processors (DSPs), which interpret the signals and send commands to control the current in the bearing's electromagnets. As a result, better electronic performance translates to a quicker reaction to external events.

Hinckley said that makers of chillers for naval vessels have recently been drawn to magnetic bearings because faster electronic performance allows the bearings to react quickly to sudden on-board shock loads. The technology is also being applied to turbomolecular pumps and rapid thermal processing equipment in the semiconductor industry, as well as to machine tool spindles, turbocompressors and turboexpanders for oil and natural gas systems.

The electronic performance boost is combining with the more traditional advantages of magnetic bearings to bring a new level of appeal to the technology, Hinckley said. Traditionally, magnetic bearings have offered high-speed operation, low friction, and cleanliness, since they require no lubrication. The combination of high speed and low friction, in particular, makes magnetic bearings suitable for such applications as 60,000-rpm vacuum pumps, as well as 10-ton turbine shafts operating at 6,000 rpm.

SKF, a maker of a wide variety of bearings, said magnetic bearings are also gaining traction in applications calling for energy efficiency. Combining the bearings with permanent magnet motors could provide an energy efficiency boost of up to 9 percent, Hinckley said.

The company stressed that engineers who are interested in magnetic bearing technology should work directly with suppliers from the beginning of the design cycle. "These are not drop-in replacements," Hinckley said. "You have to have foresight. You have to know that you want a magnetic bearing, and then you have to work hand-in-hand with the supplier."

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